These two changes you have to do in your hello project. I tried and its working fine. Here You have to mention the exact version . Hint is check your odlparent version in hello, for my case 1.7.0 ; So i ll go to this Link ; You can see there odlparent version also 1.7.0 ; So we are at the right place. In the same pom file you can see the version of openflowplugin. use that exact version.
In case your odlparent is different, lets say 1.6.3-SNAPSHOT ; then in the same link, change the branch,you will get it.
Hope you understood .plz ask me if you have any doubts,